How to use the PIP library in Blender
What you can do is just delete the python folder from the Blender directory (or move it to have a backup) and Blender will look for python preinstalled on the system. Note that the version must match (current Blender python version is 3.5.0, it works with 3.5.1 though) and environment variables need to be set (at least under Windows).

Info from here.